This invention relates to self-contained gas powered surgical staplers, and more particularly to a self-contained surgical stapler which is powered by relatively low pressure gas and which is therefore adaptable for manufacture as a disposable item. Although the invention will be illustrated and described in its application to skin and fascia type surgical staplers, it will be understood that the principles of the invention are applicable to other surgical stapler type instruments such as ligating and dividing instruments in which staple-like elements are advanced and formed as part of the operation of the instrument.
Self-contained gas powered surgical staplers are known, as shown, for example, in U.S. Pat. Nos. 3,618,842; 3,643,851; 3,662,939; 3,717,294; 3,815,476; and 3,837,555. Typically, these staplers include a replaceable cylinder which supplies gas (e.g., carbon dioxide or nitrogen) at relatively high pressure (e.g., 800 p.s.i.g.) for powering the instrument. The high pressure gas used in these staplers requires that the staplers be of relatively heavy construction which can safely accommodate the high pressures involved. Because of their construction, these instruments are relatively expensive to manufacture. These instruments are therefore generally intended to be relatively permanent and reusable.
Any reusable surgical instrument must be cleaned and sterilized between uses. Cleaning is time consuming and may require disassembly of the instrument with the consequent possibility of damage to the instrument. Sterilization requires expensive sterilization equipment. The trend is therefore increasingly toward instruments which have lower initial cost than permanent instruments, are sterile when purchased, and are disposable after a single use so that cleaning and sterilization costs are avoided.
It is accordingly an object of this invention to provide a self-contained gas powered surgical stapler which can be economically manufactured and safely handled as a disposable item.
Use of a relatively low pressure gas is advantageous to enable a stapler to be made of lighter construction and less expensive materials. This is desirable to lower the cost and make the stapler economically disposable. The stapler must, however, be capable of generating the substantial forces required to form the staples. Typically, the staples are metal wire which is partially formed prior to use and which must be further formed (e.g., bent around or crimped against an anvil) by the stapler. To generate the relatively large forces required to form the staples with low pressure gas would ordinarily require a relatively large pneumatic actuator. This is undesirable because a large actuator makes the stapler bulky and difficult to work with. In addition, a large actuator unnecessarily consumes a large amount of gas during the portion of actuator motion when relatively large forces are not required, i.e., during the first part of the actuator stroke when the staple is merely being advanced to the staple forming position. The gas which is thus effectively wasted substantially reduces the number of stapling operations which can be performed by the stapler before its gas supply is exhausted. This substantially shortens the useful life of the stapler if the gas supply is not replaceable, and even if the gas supply is replaceable, it undesirably increases the frequency with which the gas supply must be replaced.
It is therefore another object of this invention to provide a self-contained gas powered stapler which employs low pressure gas without the necessity for a large pneumatic actuator and which makes efficient use of the gas supply to increase the number of stapling operations which can be performed before the gas supply is exhausted.